The use of siloxane resins in forming protective coatings can, in certain applications, contribute properties of flexibility, impact resistance and/or weather resistance to the resulting cured coating. In some cases, a polysiloxane resin has been combined with an epoxy resin to provide improved properties of impact resistance, flexibility, corrosion resistance, and/or weatherability to the resulting coating.
Siloxane resins are sometimes used with a base resin material, e.g., an epoxy resin, and reacted by an acid or base catalyzed hydrolysis of the siloxane resin and an aminosilane, followed by condensation of the resulting silanol groups formed during hydrolysis and reaction of amine with epoxy. This reaction mechanism can be initiated by the presence of moisture conducted in the presence of an amine, and driven to completion by evaporation of alcohol formed during the hydrolysis reaction. While such epoxy-polysiloxane coating compositions are useful in forming protective coatings providing a degree of coating hardness, flexibility, impact resistance, weatherability, and corrosion and/or chemical resistance to an underlying substrate, the need to provide coatings having reduced volatile organic content (VOC) has sometimes necessitated the use of lower molecular weight resins in the formulation of such coatings.
A disadvantage, however, with using such lower molecular weight resins is that the desired above-noted coating properties are acquired by increasing the cross-link density of these resins, which can result in the coating having a reduced degree of flexibility. In certain cases, an organic material, such as an acrylic resin and/or an acrylate functional ingredient, such as an acrylate oligomer, is included in such compositions to provide improved flexibility. Such materials can also sometimes be used to reduce the drying or cure time of the coating over a broad temperature range. Drawbacks to the presence of such materials, however, can be reduced weatherability and/or stability.
It is, therefore, desired to provide coating compositions comprising silicone resins that are capable, in at least some cases, of providing a degree of coating flexibility, hardness, impact resistance, corrosion resistance and/or chemical resistance that is the same as or better than that of known polysiloxane coating compositions that include an acrylic resin and/or acrylate functional ingredients, while at the same time providing such properties within compositions that, in at least some cases, can have improved weatherability and/or stability. Moreover, it would be desirable to provide such coating compositions that, in at least some cases, are “fast-curing”.